The present invention pertains to a method and a device for producing medium pressure vapor of pressure from 30 to 80 bar during the cooling of a coal gasifier operated at temperatures from 1200.degree. to 1600.degree. C. and under pressure from 1 to 3 bar.
Methods of gasifying coal,in which temperatures and pressures of the aforementioned ranges are involved, have been known. A specifically known and widely utilized is the method which is known as Koppers-Totzek method, in which fine-grained-up to dust coal is converted into a flowing stream with respective remaining reaction components. Gasification temperatures in the coal gasifier are so adjusted that they are above the melting point of the coal ash, and deposited slag in the melted condition can be removed from the gasifier. The gasification temperature must be higher or lower in accordance with a temperature range in which various coal types melt and in accordance with the reactivity of the coal. With unreactive or inert coals, gasification temperatures used are as high as possible with reference to durability of a fire resistant lining of the gasifier. If the cooling of the reaction space of the coal gasifier becomes more intensive the higher gasification temperatures can be obtained, however, maximal permissible temperatures of fire-resistant materials of the walls in tne reaction space would not be exceeded.
It has been known that the gasifier or its reaction space has been provided with a double jacket made of sheet steel, and in which the inner jacket has enclosed a suitable reaction space, and the jacket has been equipped with a fire-resistant lining. The intermediate space between the inner jacket and the outer jacket of the coal gasifier has been utilized as a cooling space and also for producing a low pressure or saturated vapor of 3 to 5 bar. During operation within the above mentioned pressure range it has not been necessary that the gasifier or its reaction space be formed as a pressure vessel. For coals with satisfactory reaction capabilities, technically simple and inexpensive methods for coal gasification are available in practice. In order to avoid expensive pressure vessels, vapor pressure of the gasifier cooling systems has been limited to approximately from 3 to 5 bar.
The disadvantage of the above described conventional process resides in that low pressure vapor can not be efficiently processed further. In known coal gasification installations, the ratio of the production of high pressure vapor, which is generated in a waste heat recovering vessel connected to the gasifier, to low pressure or saturated vapor, produced in the cooling jacket of the gasifier, is about 1:1. Depending on the size of the reactor, the Koppers-Totzek gasifier can be adjusted so as to supply, for example, from 5 to 20 t/h of high pressure and low pressure vapor. Thus, up to now a low pressure vapor produced in the Koppers-Totzek gasifiers has burdened the entire efficiency of the installations when no reasonable applications have been offered for low pressure vapor.
It has been proposed to solve this problem by forming the Koppers-Totzek-gasifier as a tubular vessel to enable the production of vapor of higher pressures during the cooling of the gasifier. The disadvantage of such a solution is that it requires considerable investment costs which are approximately five times higher than those for a simple double jacket-gasifier.